Magnetic pick up



H. P. DONLE MAGNETIC PICK Sept. 8, 1931.

Filed April '7, 1927 INVENTOR Patented Sept. 8, 1931 UNITED STATES HAROLD r.

PATE T OFFICE DONLE, or mnnrnnitconnnotrrcur, assrsuoitrv livmsnnfessreivivrnurs. T0. RADIO INVENTIONS, Inc, A coRroR-ATIonorN w YORK.

MAGNETIC rrox .U]? Q Application filed April 7, 1927. Serial taf' suso.

, The main object of my invention is to produce a simple device which will faithfully transform the impressions or undulations of a phonograph record into alternating current pulsations of equivalent'frequencies and proportionate amplitudes.

Another-object is to produce a device of the type described above wh ch may be of such weight as to give proper pressure of 9 the stylus upon the record. v Another object is to construct a device of this type which may be readily attached to an existing phonograph. V

Another object is to permit the recorded music or other sound to bejamplified by a high quality electronic amplifier and converted into sound waves by the modern faithful loud speaker.

In my invention these objects are accom 4 go plished by means of a magnetic type needle actuated pick-up having the armaturetorsionally supported at one end anddampin'gly supported at its otherend, thus-producing a device which is sensitive, but at the same gs'time does not over-emphasize through me chanical harmonics or frequencies. I

Referring to the drawings Fig.1 is a front view of one form of the device with its cover removed. v

any particular frequency 2-'2 of Fig. 1 with the cover in place.

Fig. 3 is a sectional view along the line 33 of Fig. 1. p

Fig. 4 is an exploded view showing a number of the component parts.

Fig. 5 is a side view of the stylus holder. The base 10, which may preferably be a die-casting supports the stationary parts of the magnetic system which comprise the permanentmagnet 11 and its two L-shaped pole pieces 12 and 13. These pole pieces carry the windings 14 and 15 and the heads 16 and 17. The head 17 carries the winding terminals 18 and 18.

'ture 19.

pressthebars 3'1 and 32 apart-and so that 'readily attach the device to an existing phonograph in place of the regular mechanical reproducer. The cover 39 is provided with suitable clearance apertures for the The armature lg-has one ondsoldcred or otherwise secured to thestylus holder '20. The latter has a lSOIl of torsional pivot formed by the" spring 21. .This spring may have an opening 22 for: thelrear end ofthe stylus holder and-may be soldered to the holder. Theouter ends ofthe spring are secured to th'eipillars or supports 23 which projec't'from' the base 10.. The stylus 24 is held in place by a screw25. The spring 21 not 5 only permits the armature to vibrate according to the sound record but servesito support the armature yieldingly and thus to minimize the efiect of irregularities.

The base 10 also carries the bosses 26 which may be cast integral with'it. These bosses form seats for the-threaded parts 27 which are locked by nuts 28 and which carry the adjusting nuts 29 and 3O. The threaded rods 27 guide the bars 31 and 32. Between these bars resiliently but dainpingly held by the two pieces of flexiblerubber compressed tubing 33 and 3 1 is the forked end of the arma- The springs 35 and 36' are provided to the'nuts 30 and '31"have*at all times frictional engagement with' the threads of the posts 27 thus preventing these nuts from rep 1 'volving through vibrationi-- Fig. 2 is a sectionalyiew along the line i The 2 conductor fiexible'cords 37 may have '40 for securing it to the body or base 10.

Upon therear of the base 10 is carried thesocket 41 which may be so formed as to stylus locking screw25 andthe stylus 24.

It will be-seen that the stylus holder 20 and therefore the outer end of the armature 19 will be supported yieldingly in all directions by the spring 21 but that the action of this spring when a record is being played is largely torsional in its nature, thus producing a support in some Ways equivalent to the usual pivotal type but without the possibility of wear or rattling and Without the necessity of readjustment and sometimes replacement of parts.

The inner end of the armature 1.9 is held between the Walls of the compressed soft rubber tubes 33 and 34 which are compressed by the cross bars 31 and 32,-and this compression and hence, the damping of the armature, may be varied by adjusting the distance between these bars by means of their associated nuts 29 and 30, while the clearance between the armature and the pole tips may be varied without change in the damping by rotating the nuts 29 and 30 equally and in the same direction.

The slot 42 is provided in the rear of the armature so that considerable pressure is re quired to obtain a fair amount of damping, thus holding the. rear of: the armature firmly in place even though. the damping be but moderately heavy. Such adjustments of the damping as are necessary may be made by moving the nuts 29 and 30. I I claim:

1. An electromagnetic pick-uphaving pole pieces, an armature mounted adjacent said pole pieces, a stylus holder secured to said armature, a resilient support for said armature adjacent said stylus holder, said support permitting vibration of said armature toward and from said pole pieces and permitting said armature to move in a plane-parallel to the faces of said pole pieces, and means for damping the movement of said armature.

2. An electromagnetic pick-up comprising 'an elect-romagnet, an armature therefor, a

resilient torsional strip constituting a support for said armature, a stylus secured to one end of said armature, adjustable means for damping the movement of'the other end of said armature beyond the magnet, said stylus extending in a direction substantially normalto the plane of said strip'by which said armatureand attached parts are yieldingly supportedby said strip when said'stylus 1s in act on.

3. An electromagnetic pick-up comprising a supporting base having two posts integral therewith near one edge thereof, an

an armature member having a stylus exten sion and aresilient supporting strip secured to said stylus extension and having its ends secured to said posts, said armature being movable in a: plane parallel to the faces of the pole pieces and also movable toward and from the pole pieces.

4. An electromagnetic pick-up comprising a magnet construction having pole pieces, an armature pivotally supported near said pole pieces, said armature having a forked extension at its upper end and a stylus holder at its lower end, a tubular soft rubber damping member engaging each side of the forked extension of said armature, a yielding su port for said armature located between 1ts upper and lower ends and adjustable means for compressing said damping member against said forked extension.

5. An electromagnetic pick-up comprising an electromagnet, an armature for said magnet having pole pieces, a resilient pivotal support for one end of said armature, a damping means for the other end of said armature, a stylus extending from the end of the armaturewhich is remote from said damping means, and common means for varying the effect of said damping means and also permitting adjustment of the air gap between said armature and said pole pieces.

6. An electromagnetic pick-up comprising a magnet having pole pieces, an armature resiliently supported at one end so as to permit vibration with respect" to said pole pieces, a pair of screw-threaded posts on opposite edges of said armature, helical springs on said posts, resilient damping members on opposite faces of said armature, presser bars on said posts for pressing said springs and said damping members and adjustable nuts on said posts for adjustably holding said bars in place.

7. Anelectromagnetic pick-up comprising a magnet having pole pieces, an armature therefor, a supporting spring strip for the armature having a central passage, a stylus holder having a divided end extending thru said passage and embracing one end of said.

armature. s I

8. An electromagnetlc plck-up comprising a magnet, pole pieces ass'oclated therewith, a

coil associated with said pole pieces, an

armature mounted adjacent to said pole pieces, said armature being of thin magnetic material whereby it may be flexed, a resilient support for said armature, a stylus carrier attached to said armature adjacent to said support, damping means acting on said armature at a point remote from said support, means for adjusting the action of said damping means, and means for adjusting the position of said armature with respect to said pole faces independently of the damping action controlled by said first-mentioned means.

9. In an electromagnetic pick-up, a pivioted vibrating armature, damping means therefor, a spring member coacting with said damping means, and an adjustable clamp acting upon said damping means, said clamp acting upon the spring member in addition to said damping means, whereby the mechanical resistance to changes in the adjust ment of said clamp is greater than if said clamp acted upon said damping means only.

10. In an electromagnetic pick-up, an armature and a magnet having an air gap between said armature and said magnet, damping means bearing upon both sides of said armature, and means for adjusting the action of said damping means on both sides of the armature Without varying the airgap.

HAROLD P. DONLE. 

